Meridian drawing-board



(No Model.)

y J. B. MQELROY.

MERIDIAN DRAWING BOARD.

No. 449,049. Patented Mer. 24, 1891.

@ffy-1- as co., vnmwuwa., msumewu o e PATENT JOSIAH B. MCELROY, OFCHARLESTOWN, WEST VIRGINIA.

MERIDIAN DRAWING-BOARD.

SPECIFICATION forming part of Letters Patent No. 449,049, dated March24, 1891.

Application led January 20, 1890. Serial No. 337.565. (No model.)

To all whom it may concern.-

Be it known that I, JosIAH B. MoELRoY, a citizen of the United States,residing at Charlestown, in the county of J eiferson and State of WestVirginia, have invented a new and useful Meridian Drawing-Board, ofWhich the following is a specification.

My invention relates to improvements in drawing-boards, in which a largeprotractor is used in conjunction with a T-square and a quadrant; andthe objects 'of my invention are, first, to provide an instrumentadmitting of an inscribed drawing in boundary work of medium size, andin Work of larger size and of alignment to transfer the lines to paperon a draftsmans table, and to have an instrument so adjustable to themean bearing in work of alignment as to keep the drawing within thelimits of the paper; second, to have a board on one side of which themetallic protractor is embedded and to which the drawing-paper, ofmedium size, is fastened; third, to facilitate the adjustments and useof the several parts with reference to accurately and rapidly doing thework of plotting, drawing, and taking and describing angles. I attainthese objects by the construction illustrated in the accompanyingdrawings, in which- Figure l is a top view of the drawingboard A, as setin the case B. The circular protractor C is inserted in the board A andthe Vernier D in the case B. E is a meridian attached to the board A. Fis a draftsmans table. G is a strip fastened to the top of and parallelwith the edge of the draftsmans table F and of a height equal to that ofthe board A in the case B. K is a tangent-screw having` a right-handscrew-thread cut on one end and a left-hand one on the other. H is aclamp-screw, and I is a clamp-plate pressing on the edge of the board Aat J J in Fig. 2. The screw-sockets c f, one with a righthand thread andthe other with a left-hand, are adjustable by being suspended on thepivots e e, held by standards, one of these standards being attached tothe case B and the other to the strip T. (Shown in Fig. 2.) a is themilled head, and b the stem of tangent-screw It, one end only beingshown lines g g g g. u

Fig. 2 is a sectional view showing the center pin M, upon which theboard A revolves in the case B, and the center. pin N, iiXed in thecircular piece O, screwed to the draftsmans table, and by which the caseB, holding the board A, is made to revolve on the draftsmans table F. Pis a plate screwed to the under side of the case B, having its inneredge turned in the form of a groove, and of a diameter to give spacebetween it and the circular piece O to receive the head R of theclamp-screw S, extending through a hole in the top of the table F. T isan end view of a strip having a hole through it at one end to receivethe center pin M, and on the other end is fastened the clamp-screw H andone of the tangent-screw standards.

Similar letters refer to similar parts in both figures.

I am laware that prior to my invention drawing-boards have been madewith revolving protractors and T-squares. I therefore do not claim sucha combination, broadly; but

VhatI do claim as my invention, and desire to secure by Letters Patent,is-

l. The combination, in a meridian drawing-board, of a large protractorC, embedded in the face of and virtually being a part of the revolvingboard A, a case B, to which the Vernier D is iiXed and the tangentscrewstandard at c is fastened a reverselyout tangent-screw K, andclampscrew H, with a T-square, all substantially as set forth.

2. In a meridian drawing-board, the combination of a meridian-strip E,attached to the board A, set in the case B, which case, by

means of the center-pin N, iiXed to circular piece O, the head-plate R,and the clampscrew S, is adjustable and clamped to any angle of the lineof the strip E and the line of the strip G, attached to the tableF,substan A IOO

